/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.binary;

import java.io.UnsupportedEncodingException;

import com.mlizhi.base.codec.BinaryDecoder;
import com.mlizhi.base.codec.BinaryEncoder;
import com.mlizhi.base.codec.CharEncoding;
import com.mlizhi.base.codec.DecoderException;
import com.mlizhi.base.codec.EncoderException;


/**
 * Hex encoder and decoder. The charset used for certain operation can be set, the default is set in
 * {@link #DEFAULT_CHARSET_NAME}
 * 
 * @since 1.1
 * @author Apache Software Foundation
 * @version $Id: Hex.java 801639 2009-08-06 13:15:10Z niallp $
 */
public class Hex implements BinaryEncoder, BinaryDecoder {

/**
 * Default charset name is {@link CharEncoding#UTF_8}
 */
public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8;

/**
 * Used to build output as Hex
 */
private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

/**
 * Used to build output as Hex
 */
private static final char[] DIGITS_UPPER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

/**
 * Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
 * returned array will be half the length of the passed array, as it takes two characters to represent any given
 * byte. An exception is thrown if the passed char array has an odd number of elements.
 * 
 * @param data
 *An array of characters containing hexadecimal digits
 * @return A byte array containing binary data decoded from the supplied char array.
 * @throws DecoderException
 * Thrown if an odd number or illegal of characters is supplied
 */
public static byte[] decodeHex(char[] data) throws DecoderException {

int len = data.length;

if ((len & 0x01) != 0) {
throw new DecoderException("Odd number of characters.");
}

byte[] out = new byte[len >> 1];

// two characters form the hex value.
for (int i = 0, j = 0; j < len; i++) {
int f = toDigit(data[j], j) << 4;
j++;
f = f | toDigit(data[j], j);
j++;
out[i] = (byte) (f & 0xFF);
}

return out;
}

/**
 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
 * The returned array will be double the length of the passed array, as it takes two characters to represent any
 * given byte.
 * 
 * @param data
 *a byte[] to convert to Hex characters
 * @return A char[] containing hexadecimal characters
 */
public static char[] encodeHex(byte[] data) {
return encodeHex(data, true);
}

/**
 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
 * The returned array will be double the length of the passed array, as it takes two characters to represent any
 * given byte.
 * 
 * @param data
 *a byte[] to convert to Hex characters
 * @param toLowerCase
 *<code>true</code> converts to lowercase, <code>false</code> to uppercase
 * @return A char[] containing hexadecimal characters
 * @since 1.4
 */
public static char[] encodeHex(byte[] data, boolean toLowerCase) {
return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
}

/**
 * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
 * The returned array will be double the length of the passed array, as it takes two characters to represent any
 * given byte.
 * 
 * @param data
 *a byte[] to convert to Hex characters
 * @param toDigits
 *the output alphabet
 * @return A char[] containing hexadecimal characters
 * @since 1.4
 */
protected static char[] encodeHex(byte[] data, char[] toDigits) {
int l = data.length;
char[] out = new char[l << 1];
// two characters form the hex value.
for (int i = 0, j = 0; i < l; i++) {
out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
out[j++] = toDigits[0x0F & data[i]];
}
return out;
}

/**
 * Converts an array of bytes into a String representing the hexadecimal values of each byte in order. The returned
 * String will be double the length of the passed array, as it takes two characters to represent any given byte.
 * 
 * @param data
 *a byte[] to convert to Hex characters
 * @return A String containing hexadecimal characters
 * @since 1.4
 */
public static String encodeHexString(byte[] data) {
return new String(encodeHex(data));
}

/**
 * Converts a hexadecimal character to an integer.
 * 
 * @param ch
 *A character to convert to an integer digit
 * @param index
 *The index of the character in the source
 * @return An integer
 * @throws DecoderException
 * Thrown if ch is an illegal hex character
 */
protected static int toDigit(char ch, int index) throws DecoderException {
int digit = Character.digit(ch, 16);
if (digit == -1) {
throw new DecoderException("Illegal hexadecimal charcter " + ch + " at index " + index);
}
return digit;
}

private final String charsetName;

/**
 * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET_NAME}
 */
public Hex() {
// use default encoding
this.charsetName = DEFAULT_CHARSET_NAME;
}

/**
 * Creates a new codec with the given charset name.
 * 
 * @param csName
 *the charset name.
 * @since 1.4
 */
public Hex(String csName) {
this.charsetName = csName;
}

/**
 * Converts an array of character bytes representing hexadecimal values into an array of bytes of those same values.
 * The returned array will be half the length of the passed array, as it takes two characters to represent any given
 * byte. An exception is thrown if the passed char array has an odd number of elements.
 * 
 * @param array
 *An array of character bytes containing hexadecimal digits
 * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
 * @throws DecoderException
 * Thrown if an odd number of characters is supplied to this function
 * @see #decodeHex(char[])
 */
public byte[] decode(byte[] array) throws DecoderException {
try {
return decodeHex(new String(array, getCharsetName()).toCharArray());
} catch (UnsupportedEncodingException e) {
throw new DecoderException(e.getMessage(), e);
}
}

/**
 * Converts a String or an array of character bytes representing hexadecimal values into an array of bytes of those
 * same values. The returned array will be half the length of the passed String or array, as it takes two characters
 * to represent any given byte. An exception is thrown if the passed char array has an odd number of elements.
 * 
 * @param object
 *A String or, an array of character bytes containing hexadecimal digits
 * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
 * @throws DecoderException
 * Thrown if an odd number of characters is supplied to this function or the object is not a String or
 * char[]
 * @see #decodeHex(char[])
 */
public Object decode(Object object) throws DecoderException {
try {
char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
return decodeHex(charArray);
} catch (ClassCastException e) {
throw new DecoderException(e.getMessage(), e);
}
}

/**
 * Converts an array of bytes into an array of bytes for the characters representing the hexadecimal values of each
 * byte in order. The returned array will be double the length of the passed array, as it takes two characters to
 * represent any given byte.
 * <p>
 * The conversion from hexadecimal characters to the returned bytes is performed with the charset named by
 * {@link #getCharsetName()}.
 * </p>
 * 
 * @param array
 *a byte[] to convert to Hex characters
 * @return A byte[] containing the bytes of the hexadecimal characters
 * @throws IllegalStateException
 * if the charsetName is invalid. This API throws {@link IllegalStateException} instead of
 * {@link java.io.UnsupportedEncodingException} for backward compatibility.
 * @see #encodeHex(byte[])
 */
public byte[] encode(byte[] array) {
return StringUtils.getBytesUnchecked(encodeHexString(array), getCharsetName());
}

/**
 * Converts a String or an array of bytes into an array of characters representing the hexadecimal values of each
 * byte in order. The returned array will be double the length of the passed String or array, as it takes two
 * characters to represent any given byte.
 * <p>
 * The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by
 * {@link #getCharsetName()}.
 * </p>
 * 
 * @param object
 *a String, or byte[] to convert to Hex characters
 * @return A char[] containing hexadecimal characters
 * @throws EncoderException
 * Thrown if the given object is not a String or byte[]
 * @see #encodeHex(byte[])
 */
public Object encode(Object object) throws EncoderException {
try {
byte[] byteArray = object instanceof String ? ((String) object).getBytes(getCharsetName()) : (byte[]) object;
return encodeHex(byteArray);
} catch (ClassCastException e) {
throw new EncoderException(e.getMessage(), e);
} catch (UnsupportedEncodingException e) {
throw new EncoderException(e.getMessage(), e);
}
}

/**
 * Gets the charset name.
 * 
 * @return the charset name.
 * @since 1.4
 */
public String getCharsetName() {
return this.charsetName;
}

/**
 * Returns a string representation of the object, which includes the charset name.
 * 
 * @return a string representation of the object.
 */
public String toString() {
return super.toString() + "[charsetName=" + this.charsetName + "]";
}
}
